This invention relates to a process for laser soldering of flexible wiring, in particular, to soldering of wiring mounted on a brittle substrate.
In order to join two parts by means of soldering it has been possible to use, for a direct transmission of heat, the metallization of one part, or to transmit the heat for the soldering process indirectly over soldered strip conductors.
Spot-welding (soldering) of connections on hybrid circuits has only very recently come under consideration as a possible application for a laser. In a welding process, the materials to be welded are brought to the melting point which results in a direct joining of the two materials. A prerequisite for a permanent joint is the availability of sufficient material. When this condition is not satisfied, a soldering process must be used. For this purpose the materials must be covered with a solderable mass (soft or hard solder). In this case the laser acts as a source of heat, which operates very precisely only on the exact points to be joined. This process cannot be used to solder flexible wiring to glass substrates.